If I only knew in high school what I know now.
I'm assuming the girl you mentioned in your post was your girlfriend. If it's just a girl you're seeing or have gone on a few dates with, this does not apply.
In any relationship, both the man and the woman should feel comfortable enough to talk about what they want in the relationship, sex and anything related to sex included.
I know it probably will feel strange, or uncomfortable, to bring up a subject as delicate as sex with your girl. Especially since it sounds like you've never done it before. So to make the process easier, here's the best advice I have to offer.
First, girls (especially if you've been dating for an extended period of time) usually carry the same desires that men have, but don't count on her EVER verbalizing what she really wants from you, 95% of women (the younger the girl the more this applies) out there is too shy to even hint at what her sexual desires are. Basically, girls want to fool around with boys as much as boys want to fool around with girls. Except we're the men, so it's our job to act on it. I've dated quite a few girls throughout high school and my first three semesters at college. In that length of time, there was only once that a girl ever initiated anything sexual, and she was probably a little tipsy. So pretty much if you're going to wait for your girl to make the first move, take a jacket, you're gonna be out in the cold for awhile.
This doesn't mean she doesn't want to fool around. She probably just doesn't know what you want. And if she cares about you she'll probably want to keep you happy. All you really have to do is step up, be the man, and tell her exactly what it is you want from her. At that point more likely than not you'll get what you asked her. On the other hand, she may not be ready to take the next step like that and hopefully she'd feel comfortable enough with you to tell you at that point.
I know what you're thinking. But Jared, if I tell a girl that I want my d*ck sucked, isn't that a huge mistake? Won't she think that's all I want from her, and won't I sound like the biggest douchebag in the world? Well, maybe. But as long as you don't go about saying it the wrong way, and the girl trusts you, then not at all. Of course, how do you go about gaining a girl's trust in the first place? Show her that you care, be there for her...you get the idea. So really if you've done your fair share of all that, then she should know by now that a blowj*b isn't all you want from her.
If you still don't wanna verbalize your thoughts to her, then eating her p*ssy would pretty much guarantee you head in return. If you've never done that and wouldn't know how to go about it, sounds like it's time to make a new post. But just talk to her about it. You don't get a date to the movies by putting the girl's hand on a movie ticket do you? No, you ask her. So putting her hand on your **** may not get the message across.
That's all I have, good luck dante